The tensile properties of the as-cast microstructures of four aluminum alloys ­ one AA5083 alloy and three AA6061 alloys from different sources ­ have been measured at temperatures around and above the relevant non-equilibrium solidus temperatures. It was found that tensile properties differed between the alloys tested and were dependent on the solid grain morphology, the distribution and continuity of the liquid phase and the deformation rate. It was suggested that two temperature regimes of semi-solid tensile properties exist for the alloys tested.